1. Field of the Invention
The embodiments of the present invention relate generally to a filter housing assembly.
2. Background of the Invention
Cleanrooms are utilized in many industries for contamination control and to improve product yields. A plurality of filters, typically mounted in the ceiling of the cleanroom, are configured to remove particulate from air entering the cleanroom at a predetermined efficiency selected based upon the cleanliness requirements of the activities performed in the cleanroom. As particulates load the filtration media disposed in the filter, the airflow through the filter decreases as the pressure drop across the filter increases. Once the filter reaches a critical pressure drop, the filter is typically replaced.
On other applications, replacement of filters is scheduled based on time or processes performed within the cleanroom. For example, in many pharmaceutical and biotech cleanrooms, periodic replacement of filters is required to meet regulatory or owner specifications. To facilitate efficient replacement of the filter, a hood (housing) is typically mounted in the cleanroom ceiling in which the filter may be readily removed and replaced.
Ducted supply hoods with roomside replaceable filters are commonly used in pharmaceutical applications for cleaning supply air to cleanroom manufacturing and process areas, as well as to laboratory areas. Most of these hoods are supplied with adjustable dampers that allow customers to regulate the airflow without having to remove the filter from the hood. The most common types of dampers are guillotine, opposed blade and butterfly types. When completely closed, these dampers essentially stop the flow of air to the hood. In many cases, the leakage through a closed damper is negligible in terms of flow rate, but is significant when considered in the terms of contamination of a cleanroom.
Because these types of dampers do not provide a seal (i.e., are not leak-free or bubble-tight), they are inadequate when it comes to decontamination processes that require complete isolation of the cleanroom. For example, during routine testing and validation of filters installed in a pharmaceutical facility, one or more filters may be found damaged, leaking and/or requiring replacement. When a technician removes that filter from the hood, the “seal” between the cleanroom and the contaminated plenum and supply ducts upstream of the removed filter is broken. When the new filter is installed, the “seal” between those two areas is restored, but the cleanroom has already been contaminated by air and particulate entering the cleanroom from the contaminated area of the plenum and supply ducts. Thus, the facility owner must perform a decontamination process of the entire room before resuming cleanroom operations. This is a very time-consuming and costly process.
Therefore, there is a need for a filter housing assembly having improved sealing capabilities.